Rumer Willis' Broadway debut has been postponed nearly a month to allow her the necessary time to fully recover from multiple stress fractures to her foot, the producers of Chicago announced.Chicago veterans Amy Spanger and Dylis Croman will play Roxie Hart until Willis assumes the role.With a book by Fred Ebb and Bob Fosse, music by John Kander and lyrics by Fred Ebb, Chicago is the longest-running American musical in Broadway history.